An epoxy resin is conventionally widely used, in the form of an epoxy resin composition in combination with a curing agent or a curing catalyst, in the fields of electronic materials such as an adhesive, a high refractive index layer of an anti-reflective coating (such as an anti-reflective coating for a liquid crystal display), an optical thin film (such as a reflector), a sealant for an electronic component, a printed wiring board and an interlayer insulating film material (such as an interlayer insulating film material for a build-up printed board). In the fields of these electronic materials, in application to a printed wiring board or an interlayer insulating film material, a low dielectric constant is required, in addition to high adhesiveness to a substrate, a hard coating property, heat resistance, high transparency to visible light and the like, in recent years for inhibiting electric signal delay or adjusting capacitance of an electronic device.
For obtaining reliability such as heat resistance and light resistance required of such an electronic material, an epoxy compound needs to have a rigid molecular skeleton. In general, however, a compound having a rigid molecular skeleton and having high interaction between molecules is likely to be in the form of a solid or a high viscosity liquid. Therefore, an epoxy resin composition using an epoxy compound having a rigid molecular skeleton has a problem of poor handleability because of the increased viscosity.
In particular, in the fields of semiconductors and liquid crystals further refined in recent years, a resin layer of an epoxy resin or the like is coated, in many cases, on an upper layer having a fine irregular structure formed by lithography or nanoimprint. If a used epoxy resin composition has a high liquid viscosity, however, the resin composition cannot bury the fine irregular structure when coated, which adversely affects a process performed thereafter.
Besides, in addition to the aforementioned properties, a low dielectric constant is required in recent years for inhibiting electric signal delay or adjusting capacitance of an electronic device. An epoxy resin cured product has high polarity in general, however, and hence it is difficult to attain a sufficiently low dielectric constant.
As a liquid epoxy compound for obtaining an epoxy resin cured product having high heat resistance, high transparency and the like, an epoxy compound having an isocyanurate skeleton is conventionally known (for example, Patent Document 1).
Besides, as a method for lowering a dielectric constant of an epoxy resin cured product, a method for lowering a dielectric constant of a cured product in which a hollow particle is added to an epoxy resin composition for causing a cured product obtained from the composition to include an air layer is known (for example, Patent Document 2).